Controlling the heat exchangers of air condensation apparatus



Jan. 25, 1966 I L. HELLER ETAL 3,231,013

CONTROLLING THE HEAT EXCHANGERS OF AIR GONDENSATION APPARATUS Filed Jan.27. 1961 4 Sheets-Sheet 1 F/g. Z

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CONTROLLING THE HEAT EXCHANGERS OF AIR CONDENSATION APPARATUS Filed Jan.27. 1961 4 Sheets-Sheet 5 INVENTORS M32 L0 HEZLER, mszm mean BY Jma:.3000;

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CONTROLLING THE HEAT EXCHANGERS OF AIR CONDENSATION APPARATUS Filed Jan.27, 1961 4 Sheets-Sheet 4.

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United States Tatent C 3,231,013 CONTROLLING THE HEAT EXCHANGERS OF AIRCONDENSATION APPARATUS Laszl Heller, Laszl Forg, and Janos Bdas,Budapest,

Hungary, assignors to Licencia Talalmanyokat Ertekesito Vallalat,Budapest, Hungary Filed Jan. 27, 1961, Ser. No. 85,339 4 Claims. (Cl.165-97) This invention relates to controlling the heat exchangers of aircondensation apparatus.

As is known, in the so-called air condensation apparatus of power plantsthe exhaust steam of turbines is condensed indirectly by means ofatmospheric air. Such apparatus are used on sites where no suificientquantities of cooling water is at disposal. Their characteristic featureis that they operate without any loss of water, due to the Water servingfor cooling purposes being circulated in a closed system. Condensationof the exhausted steam of the steam turbine is effected in a jetcondenser by cooling water, naturally with the result of the coolantbeing warmed-up. The hot cooling water is Withdrawn from the condenserby means of a circulating pump and supplied into a heat exchangerapparatus of large surface swept by a stream of atmospheric air. In suchheat exchanger apparatus the cooling water is cooled down whcreafter itis returned into the jet condenser for being mixed with exhaust steam asbefore.

The cooling output of the heat exchangers of such apparatus is to becalculated so as to enable it to cool down the cooling Water to anextent which is necessary for an economic operation of the steam turbineeven if the latter is under maximum load and, consequently, a maxi- ;mumamount of steam has to be condensed and, at the same time, thetemperature of the atmospheric air reaches its upper limit.

Thus, the output of the heat exchanger apparatus is too great Wheneverthe amount of steam introduced into thejet condenser is less than themaximum value or else the temperature of the atmospheric air is inferiorto the maximum temperature value taken as basis of dimensioning. In suchcases, the cooling water would excessively pheric air is below freezingpoint.

I At present, two methods are known for controlling the thermal outputof heat exchanger apparatus associated with air condensation systems.One of these methods consists in that the amount of cooling watercirculated across heat exchanger elements is decreased whereby,

however, the heat transfer coefiicient of the heat exchanger apparatusand the mean temperature difference between air and water diminish sothat also the thermal output of the heat exchanger apparatus decreases.However, by means of such type of control the temperature of the coolingwater withdrawing from the heat exchanger constantly decreases with thediminishing amount thereof sothat such a control may be applied onlyuntil the temperature of the cooling water withdrawing from the heatexchanger apparatus approaches the freezing point.

According to the other method suitable for controlling the output ofheat exchanger apparatus of air condensa- .tion systems a part of theheat exchanger apparatus is disconnected with the circulation of thecooling water in which case the dicsonnected heat exchangers do not ex-Such system of control is, principally, capable to alter the output ofthe heat exchanger apparatus within any limits. However, an economicestablishment of heat exchanger apparatus requires the number ofdisconnectable parts to be restricted to a minimum. Viz., eachindividually disconnectable heat exchanger part requires a great numberof expensive armatures or fittings associated with it so that anexcessively great number of heat exchanger parts entail a considerableincrease in investment costs. Apart from such surplus expenses theaforesaid method of control unnecessarily increases the number offillings which being delicate operations are undesirable. Namely, if inthe course of filling subsequent to a previous emptying air remains inone of the heat exchanger passages, it prevents there the setting-in ofcirculation of the cooling water with the result of a freezing-in of therespective heat exchanger element.

Neither a simultaneous application of both aforesaid control methodsgives the possibility of adjusting the temperature of the waterwithdrawing from the heat exchanger apparatus to an actually requiredoptimum value at any quantities of steam to be condensed and at anytemperatures of atmospheric air.

The main object of the present invention is to propose a new apparatusfor the control of the thermal output of heat exchanger apparatus theuse of such control with known devices permitting the temperature of thecooling water supplied by the heat exchanger apparatus to al-- wayscorrespond to the desired optimum value.

The new control method according to the invention is based on the ideaof the possibility of running two-way cross-flow heat exchangerapparatus in cross counterflow connection as well as in cross parallelflow connection, respectively.

As is known, heat exchangers used with air condensation systems arebuilt up of a plurality of heat exchanger elements each of whichreceives the cooling water at its bottom portion and conducts it througha group of finned parallel tubes to a top portion. Here, a returnchamber serves for reversing the flow direction of the cooling waterwhich flows through a second group of tubes of the heat exchanger againto the bottom portion thereof where it withdraws through an outlet stub.In both groups of tubes or heat exchanger sections the air flow is ofthe cross-flow types.

In case of such heat exchanger elements, the connection is labelled ascross parallel flow if the admitted cooling water contacts fresh air inthe first one of the aforesaid groups of tubes or heat exchangersections whereas in the second one it is the cooling water alreadycooled down and the warmed-up air which contact each other in across-flow type heat exchange (FIG. 1).

Cross counterflow connection consists in an arrangeent wherein thecooling water introduced into the heat exchanger element first contactsair already warmed-up in the second section or group of tubes, a contactwith fresh air taking place in the latter (FIG. 2).

Furthermore, it is known that the thermal performance of heat exchangersis less in cross parallel fiow connection than in cross counterflowconnection under otherwise identical conditions.

Such variety of possible heat exchanges oifers a further possibility ofadjusting the output of heat exchangers used with air condensationsystems. Viz., besides both aforesaid methods of adjusting the thermaloutput also use is made of wholly or partly switching over a heatexchanger apparatus from cross counterfiow to cross parallel fiotw typeof connection.

The heat exchanger elements have to be constructed so as to dischargethe water immediately upon stopping of its circulation. Namely, ifcirculation of the cooling water is stopped in the heat exchangersbecause of stopping of its circulating pump and the temperature of thecooling air happens to be below the zero point, the cooling waterquickly freezes in the tubes of the heat exchangers which will bedestroyed thereby. Therefore, it is important that the cooling water beautomatically drained oif immediately upon stopping of the circulatin'gpump of the heat exchanger apparatus. Obviously, the means serving forthe aforesaid switching-over must not prevent an automatic drainage ofthe respective heat exchanger element and of the piping associatedtherewith.

A further requirement in connection with heat exchangers of aircondensation systems is that the pressure of water therein be anywheresuperior to the atmospheric pressure since this is the only way towarrant that no air enter the heat exchanger at probably defectiveplaces. Moreover, such places should immediatelybe indicated by waterspouting therefrom. Thus, a further object of the invention consists inthe provision of a switching-over apparatus which prevents the pressureof the cooling water to drop below the atmospheric pressure anywhere inthe heat exchanger apparatus.

Finally, it is required with heat exchangers of the above described typethat any switching-over thereof be quickly feasible so that circulationof the cooling water be interrupted only for a time period of at mostone to two minutes.

The invention will hereinafter be described in closer details by takingreference to the annexed drawings FIG. 3 of which shows, by way ofexample, an embodiment of a heat exchanger apparatus according to theinvention capable of being switched over from cross counterfiow to crossparallel flow connection and vice versa, FIGS. 1 and 2 illustrating thealready explained principles of such connections.

FIG. 4 shows an embodiment of the invention for operating a plurality ofheat exchange elements. FIG. 5 is a schematic diagram of a hydraulicsystem for switch over of the heat exchange apparatus of the invention.

FIG. 3 shows an element of a heat exchanger suitable for aircondensation systems referred to above. It consists of a pair of groupsof tubes or sections 13 and 14 serving for cooling down a coolant, i.e.,water introduced via a" supply pipe conduit 2 and returned to anot-represented jet condenser of the system via a return pipe conduit 3.Cooling down of the water is effected by atmospheric air flowing, in theinstant case, in the direction of arrows '1. The top portion of therepresented heat exchanger element is formed by a return chamber 5whereas at the bottom portion thereof an inlet stub 4 and an outlet stub6 for introducing and withdrawing, respectively, of the cooling waterare provided. In operation of the heat exchanger element in a crosscounterfiow type of contact between cooling water and air the formerflows from the pipe conduit 2 through the stub 6 and section '14 of theheat exchanger into the return chamber 5 which purpose various valvemeans such as gate valves or sluices are provided. Viz., stub 4 isconnected to pipe conduits 2 and 3 by means of valves 7 and 8, whereasstub 6 communicates with both pipe conduits 2 and 3 through valves and9, respectively.

A tank 15, serving for storing the water drained olf from the heatexchanger element, is connected to the conduits of the cooling water bypipe conduits 16 and 17 upstream the valves 8 and 10, respectively. Thepipe conduits 16 and 17 comprise valves 18 and 19, respectively.

Switching-over of the above described apparatus from cross counterflowconnection to cross parallel flow connection is carried out in thefollowing manner:

As has been shown, in case of cross counterflow operation, the coolingwater is introduced into the heat exchanger element through valve 10and. stub 6 whereas it withdraws therefrom through stub and valve 7,valves 8 and 9 as well as valves 18 andj 19 then being closed. In orderto switch over first valve 7 is to be closed whereafter valve 8 maybeopened. This sequence of handling the valves prevents the pressure inthe cooling element to drop below the normal operating pressure duringswitching-over. Then, valve 10 is closed and finally valve 9 openedwhereby switchin -over to cross parallel flow connection has beencarried out. In this case, the cooling water flows from pipe conduits 2through valve 8 and stub 4 first into heat exchanger section 13 andtheninto heat exchanger section 14 wherefr om it withdraws through stub6 and valve 9 into the'return pipe conduit 3. Valves 7 and 10 as well asvalves 18 and 19 are now closed.

Switching over from cross parallel flow connection to cross counterflowconnection, that is, from a lower heat out-put to a higher thermaloutput is eifected by'closing valve 9 and opening valve 10. Then, valve8 is closed whereupon valve 7 is opened.

FIG. 4 shows an exemplified embodiment of the invention wherein thegroup of valves=7, 8, 9 and 10 as well as of the valve means 15, 16, 17,18, 19 serve for operating a plurality of heat exchanger elements ratherthan one of them, such elements being arranged in parallel connection bymeans of pipe conduits 22 and 23, the stubs 4 being connected to pipeconduit 22whereas the stubs 6 are connected to pipe conduit 23. Themeans serving to switch over and drain oil are likewise connectedto thepipe conduits 22 and 2-3. In the instant case, by switching over thegroupof valves 7, 8, 9 and It) in the manner described in connectionwit-h FIG. 3 all heat exchanger elements connected to the pipe conduits2 2 and 23 are switch over from one type of operation to the other typethereof. i I

In FIG. 5, a structure is shown wherein the switchover is effected byhydraulic means. In this embodiment, valves 7, 8, 9 and' 10 correspondto the valves of FIG. 3, and the heat exchanger element is not shown.The valves are illust'ratively shown in the condition in which valves 8and 9 are closed and valves 7 and '10 are open (cross counterflowcondition).

A supply of oil is maintained in reservoir 34 and is pumped underpressure by pump 33 from reservoir 34 through change-over valve 31 towork cylinder 35 on the right or left of piston 35a, depending upon thep0sition of valve 31. In the-illustrated position of switch 32, the highpressure oil enters cylinder on the right of piston 35a and drives cammember 36 coupled to piston 35a to the left (arrow 38'). Cam member 36is shown at the beginning of its stroke to the left.

Cam member 36 controls slide valves 37a, 37b, 37c and 37d whichrespectively control valves 7, 8, 9 and 10. In the illustrated rightposition of cam member 36,

the pistons of slide valves 37b and 37d are depressed and the pistons ofslide valves 37a and 370 are elevated. In the left position of cammember 36, the positions of the slide valves are reversed.

. The oil from pump 33 is also led through branch lines through thecasings of the slide valves and back to' reservoir 34. The casings areconnected by further branch lines to the casings of valves 7, 8, 9 and10. In the illustrated arrangement, the oil flow is such as to maintainvalves 8 and 9 closed and valves 7 and 10 open. It will the apparentthat the various air flow circuits are reversed when member 36 is movedto the left so as to open valves 8 and 9 and close valves 7 and 10.

When valve 32' is moved to position 31, the valves are restored to theirillustrated condition.

It will be further noted that the cams on member 36 are positioned sothat on movement of member 36 to the left, the sequence of valveopenings and closings is as follows: initially, valves 8 and 9 areclosed and valves 7 and 10 are open. Then valve 7 is closed. Next valve10 is closed. Finally, valve 9 is opened. On reverse movement of member36, the desired sequence of valve operations will also be obtained.

What we claim is:

1. In a heat exchanger for cooling water with atmospheric air, a pair ofheat exchanger sections through which water to be cooled is adapted toflow, said sections being arranged beside each other with one of saidsections in advance of the other with respect to the direction of airflow so that said one section is contacted by atmospheric air before theother section, said heat exchanger sections respectively having adjacenteach other a pair of communicating ends through which said heatexchanger sections communicate directly with each other, and said heatexchanger sections also having adjacent each other a pair ofnon-communicating ends opposed to said communicating ends, respectively,a pair of tubular stubs respectively communicating with saidnon-communicating ends of said heat exchanger sections, a supply conduitfor supplying warm water to be cooled, a return conduit for withdrawingcooled water from the heat exchanger sections, a pair of inlet valvesboth communicating with said supply conduit and respectivelycommunicating with said tubular stubs, and a pair of discharge valvesboth communicating with said return conduit and respectivelycommunicating with said tubular stubs, whereby said valves may be movedbetween open and closed positions providing a flow of water from saidsupply conduit first through said one heat exchanger section and thenthrough said other heat exchanger section, to provide a cross parallelflow, or first through said other heat exchanger section and thenthrough said one heat exchanger section to provide a cross counterflowin order to increase the thermal performance as compared to the thermalperformance during cross parallel flow.

2. In a heat exchanger as recited in claim 1, a pair of dischargeconduits respectively communicating with said tubular stubs, and a pairof additional valves respectively connected operatively to said pair ofdischarge conduits for maintaining them closed during normal operationof said heat exchanger sections, said additional valves when openquickly discharging both of said sections through said dischargeconduits.

3. In a heat exchanger as recited in claim 1, said sections togetherwith said tubular stubs and valves forming a unit which is connected tosaid supply and return conduits with all of said valves branching fromsaid supply and return conduits and with said supply and return conduitsextending uninterruptedly past said unit so that a plurality of unitsmay be served by said supply and return conduits even if all of saidvalves are closed to take said unit out of operation.

4. In a heat exchanger as recited in claim 1, means cooperating withsaid valves for opening an inlet valve connected to one stub and adischarge valve connected to the other stub while closing the other twovalves, said latter means first closing a previously opened dischargevalve, then opening a previously closed inlet valve, then closing apreviously open inlet valve, and finally opening a previously closeddischarge valve in order to change the direction of flow of waterthrough said heat exchanger sections.

References Cited by the Examiner UNITED STATES PATENTS 2,844,319 7/1958McGrath 236-1 3,008,695 11/1961 Van Melle 50 FOREIGN PATENTS 809,5102/1959 Great Britain.

ROBERT A. OLEARY, Primary Examiner.

HERBERT L. MARTIN, CHARLES SUKALO,

Examiners.

1. IN A HEAT EXCHANGER FOR COOLING WATER WITH ATMOSPHERIC AIR, A PAIR OFHEAT EXCHANGER SECTIONS THROUGH WHICH WATER TO BE COOLED IS ADAPTED TOFLOW, SAID SECTIONS BEING ARRANGED BESIDE EACH OTHER WITH ONE OF SAIDSECTIONS IN ADVANCE OF THE OTHER WITH RESPECT TO THE DIRECTION OF AIRFLOW SO THAT SAID ONE SECTION IS CONTACTED BY ATMOSPHERIC AIR BEFORE THEOTHER SECTION, SAID HEAT EXCHANGER SECTIONS RESPECTIVELY HAVING ADJACENTEACH OTHER A PAIR OF COMMUNICATING ENDS THROUGH WHICH SAID HEATEXCHANGER SECTIONS COMMUNICATE DIRECTLY WITH EACH OTHER, AND SAID HEATEXCHANGER SECTIONS ALSO HAVING ADJACENT EACH OTHER A PAIR OFNON-COMMUNICATING ENDS OPPOSED TO SAID COMMUNICATING ENDS, RESPECTIVELY,A PAIR OF TUBULAR STUBS RESPECTIVELY COMMUNICATING WITH SAIDNON-COMMUNICATING ENDS OF SAID HEAT EXCHANGER SECTIONS, A SUPPLY CONDUITFOR SUPPLYING WARM WATER TO BE COOLED, A RETURN CONDUIT FOR WITHDRAWINGCOOLED WATER FROM THE HEAT EXCHANGER SECTIONS A PAIR OF INLET VALVESBOTH COMMUNICATING WITH SAID SUPPLY CONDUIT AND RESPECTIVELYCOMMUNICATING WITH SAID TUBULAR STUBS, AND A PAIR OF DISCHARGE VALVESBOTH COMMUNICATING WITH SAID RETURN CONDUIT AND RESPECTIVELYCOMMUNICATING WITH SAID TUBULAR STUBS, WHEREBY SAID VALVES MAY BE MOVEDBETWEEN OPEN AND CLOSED POSITIONS PROVIDING A FLOW OF WATER FROM SAIDSUPPLY CONDUIT FIRST THROUGH SAID ONE HEAT EXCHANGER SECTION AND THENTHROUGH SAID OTHER HEAD EXCHANGER SECTION, TO PROVIDE A CROSS PARALLELFLOW, OR FIRST THROUGH SAID OTHER HEAD EXCHANGER SECTION AND THENTHROUGH SAID ONE HEAT EXCHANGER SECTION TO PROVIDE A CROSS COUNTERFLOWIN ORDER TO INCREASE THE THERMAL PERFORMANCE AS COMPARED TO THE THERMALPERFORMANCE DURING CROSS PARALLEL FLOW.